Cylinder head for two-cycle doublebore-cylinder internal combustion engines



Dec. 27, 1938. f A RTMANN 2,142,004

CYLINDER'HEAD FOR TW YCLE DOUBLE-B -CYLINDER INTERNAL COMBUSTION ENGIN Filed Aug. 16, 1937 2 Sheets-Sheet l Dec. 27, 1938. A- PORTMANN 2,142,004

CYLINDER HEAD FOR Two-CYCLE DoUBLE-BoRE-CYLINDER INTERNAL COMBUSTION -INES Filed Allg. '16, l 2 Sheets-Sheet 2 n m m W f4 W www?? Patented Dec. 27, 1938 UNiTED. sms

yATWT GFFiE 2,142,004 v CYLINDER imapl For. Two-crocs. DOUBLE- EURE-CYLINDER TION ENGINESV INTERNAL COMBUS- Application August 16,

1937, Serial No. 159,413

In Germany August 17,'1936 1 claim.

This invention relates to two-cycle doublebore-cylinder internal combustion engines.

In two-cycle double-bore-cylinder internal combustion engines, the clearance between the piston and the cylinder head as well as the space interconnecting the two bores of the cylinder constitute parts of the compression space. In order to obtain apredetermined value of compression pressure, as required for initiating the ignition, it is necessary to provide for acertain compression space volume which with double-borecylinders is, however, obtainable with accuracy only with difhculty,v due to the particular shape of the compression space, particularly in cases where the cylinder head is not detachably arranged and consequently the limiting surfaces of the communication passage extending between the cylinder bores are scarcely accessible for precise machining. On the other hand, if the cylinder head is detachably arranged, it may easily happen that the connection between the cylinder head and the cylinder end becomes loose, so that the safety of operation is impaired, that is, leakage of cooling water to the outside or into the interior of the cylinder sets in, when water cooled engines are involved.

Furthermore, since in two-cycle double-borecylinder internal combustion engines the fuel is naturally injected through a single nozzle, into the communication passage intercommunicating with the cylinder bores and constituting the major part of the combustion space and into the adjoining portions of the cylinder space swept by the piston, it is soy to speak unavoidable that jets of fuel impinge on cooled wall portions, due to the fact that in contrast with the more usual internal combustion engines the bulk of the jets of fuel cannot be directed against the hot piston end surface.

According to this invention, these drawbacks as well as the dilculties encountered in precisely machining the compression space, as previously mentioned, are met at the same time by arranging approximately in the middle between the two cylinder bores a lid-like one-part or sectional insert in a cylindrical aperture of the cylinder head, the insert limiting the communication passage at least upwardly and on both sides thereof.

The surface of this one-part or sectional insert facing the combustion space can be trimmed with the required accuracy and the insert permits to prevent the fuel jets from impinging on cooled wall portions, as desired. Due to the fact that only a relatively small portion of the surface of (Cl. 12S- 53) the insert is subjected -to the combustion pressure, a strong connection between the insert and the cylinder can be obtained.

In the accompanying drawings constructional forms of the invention are shown by way of example only, in which Fig. 1 is a section taken through both bores of a cylinder of a double-bore-cylinder internal combustion engine according to the inventicn;

Fig. 2 is a section taken along the line II-II of Fig. 1;

- Fig. 3 is a section taken at'right angles to the picture plane of Fig. 1 along the line III- III of the latter.

Figs. 4 and 5 each represent a different modiiication of the construction shown in Fig. 3;

Fig. 6 is a modification of the constructional form of the invention as shown in Fig. l, and

Fig. '7 shows another modification of Fig. 3.

In the constructicnal form of the invention as shown in Figs. 1 to 3, the pistons a1, a2 of a double-bore-cylinder b each cooperate with a different bore of the latter. The pistons a1, a2 are operatively connected with the engine crankshaft in a manner known per se (not shown). Between the cylinder b and the water jacket d thereof the cooling water h is retained. Obviously, cooling ribs for air cooling purposes may be provided instead of this water jacket. Round an axis of the double-bore-cylinder common to both bores thereof a sectional insert g, lc is disposed in the cylinder-head b1, the upper part g of the insert limiting the communication passage or channel i upwardly along its open side, and the lower part lc of the insert limiting this passage laterally and downwardly, as at n. The insert is iitted in a cylindrical aperture of the cylinder head with radial play.

The upper part y contains the water cooling chamber h1; by the expression above, as herein used, being meant that the respective part of the engine is situated remote from the crankshaft. It will be readily seen that the surface y1 provided on the upper insert part y and facing the combustion space can be easily machined with perfect accuracy and that further the side walls m of the cylinder (Fig. 3) next to the communication passage i are protected by the naps k1 of the lower part lc of the insert, the same as the lower side of this passage is protected by the portion n of the part k of the insert.

The fuel jets y, the axis of projection of which is situated in the line II-II, thus impinge on these surfaces, which are much hotter since they are not directly cooled, so that the combustion and the utilization of the fuel are effected in a more thorough manner. The lower cooled down part lc of the insert can be readily interchanged after the upper part Ag of the insert has been disconnected and removed.

In Fig. 2, which is a sectional plan view of Fig. 1, the arcuate shape of the seat k2 for the ap k1 on the lower part k of the insert and the straight smooth passage formed by the flaps k1 for the scavenging air are plainly evident.

Fig. 4 shows a modification of Fig. 3 in that the protecting lining n for the web l extending between the cylinder bores is omitted and the lateral flaps ki are united with the upper part of the insert.

Fig. 5 shows a well rounded-olf cross sectional shape of the communication passage i in the insert g, lc which shape facilitates the passage of the scavenging air.

Fig. 6 discloses how the upper part g of the insert can be constructed asymmetrically with a view of obtaining a projection, at g2, which facilitates the scavenging of the exhaust cylinder.

In Fig. '7, it is evident that the lower part k of the insert can be united with the upper part thereof into one piece p and that the upper limiting wall o of the communication passage i may be made plane instead of concave Yas shown in Figs. 1 and 3, for facilitating the machining thereof. V

By construction the surface g1 in vaulted fashion the advantage is obtained that `a greater length is provided for the fuel jets which are directed towards the portion n.

It is evident that the insert according to the invention can be applied for cases also where the cylinder head b1 is removable and thus extends across both cylinder bores, which construction brings with it the advantage that the interchanging of the parts subjected to high heat straining is facilitated.

I do not limit myself to the particular size, shape, number or arrangement of parts as shown and described, all of which may be varied without going beyond the scope of my invention as shown, described and claimed.

What I claim is: f

In a cylinder head arrangement for two-cycle internal combustion engines, an apertured cylinder head, two cylinder bores extending collaterally in spaced relation and opening endwise to said cylinder head, a communication channel open along one side thereof interconnecting said two bores at said open ends of the same, a sectional lid-like insert `arranged in an aperture in said cylinder head substantially concentrically with the central axis between said two cylinder bores, said insert comprising an outer insert part limiting said channel at said open side of the latter, and an inner insert part constituted by an inner web and two flaps connected with said web laterally of said channel, said web and said flaps limiting the bottom and both lateral sides of said channel and lining the water cooled surfaces of said channel adjacent to said inner insert part in the inserted position of the latter in said head.

AUGUST PORTMANN. 

